The present invention relates to an apparatus for feeding liquid adhesives to nozzle applicators, of the type used for example in the cigarette making industry, for applying a thin layer of adhesive on the paper web which is wrapped around the tobacco rod.
The apparatuses of the known type substantially comprise a tank for the liquid adhesive and a pump for feeding the said adhesive under pressure to a nozzle applicator. Usually, the pump is of the peristaltic type, due to the fact that, in peristaltic pumps, the liquid adhesive does not come into contact with the driving components of the pump, which therefore reduces to the minimum the cleaning maintenance of the pump at the end of the working day, and consents its inactivity even for long periods of time, without any damages.
The known type apparatuses presents however at least two disadvantages. The first disadvantage derives from the fact that usually the liquid adhesive contains entrapped in it bubbles of air or other gases which, upon reaching the nozzle applicator, cause a discontinuity in the spraying of the adhesive.
A second disadvantage is represented by the fact that the peristaltic pumps present, due to their characteristic features of operation, a delivery having a discontinuous (pulsating) flow rate, which consequently affects the spraying of the nozzle applicator.
The above and other disadvantages of the known type apparatuses are eliminated by the feeding apparatus according to the present invention, which proposes the interposition, between the peristaltic pump and the nozzle applicator, of a device for expelling the gases from the liquid adhesive, which eliminates the bubbles entrapped in the adhesive, in combination with a pressure chamber for the degasified adhesive, acting as a buffer for compensating the discontinuous delivery of the peristaltic pump.
The characterizing features of the invention and the advantages deriving therefrom will appear evident from the following description of a preferred embodiment, made with reference to the attached drawings.